—Geoff Geoffrion, Merrimack, New Hampshire As your spiders haven’t been thriving for years in a damp basement with a host of creepy crawlers for munching, and they didn’t arise spontaneously, they are likely entering from outdoors through unnoticed portals and then eating tiny creatures that enter through the same places they did. Their prey itself contains moisture, and the common house spider can survive on very little food and water. Not that your place is exactly spider heaven.